The major emphasis of this laboratory continues to be the detection, characterization, role and modification of immune complexes in human disease. Further evidencehas been obtained that low levels of complement in serum and serous cavities in patients with systemic lupus erythematosus (SLE), adult rheumatoid arthritis (RA), and juvenile rheumatoid arthritis (JRA) may be the reseult of in vivo complement fixation by immune complexes. These abnormalities will be ffurther characterized by analysis of complement components C1,4,2,3,5,6,7,8 and 9, as well as the properdin system, not only in patients with low CH50 levels, but also in patients with elevated levels. These complement data will be correlated to clinical parameters being following in these patients. The subgroups of human (gamma G1,2,3, and 4) are being characterized in patients with recurrent infections and lymphoproliferative disorders. Lymphocytes from normals and from patients with both benign and maliganant lymphocytosis and from patients with rheumatic diseases are being characterized as to B and T lymphocytes by rosetting techniques with SRBC and EAC and surface immunoglobulins gamma G, A, M.D. and E. This information will be correlated to different clinical features of these disorders. Antisera are being prepared to tissues from patients with SLE, RA and JRA.